D-MSS-DS-23 Dell Midrange Storage Solutions Design 2023 Questions and Answers

According to Dell PowerStore documentation (PowerStore OS 2.0+):

A Base Volume Family logically groups:

Original volume (source)

Snapshots (point-in-time copies)

Thin clones (writable snapshots)

Replication targets (synchronized copies for disaster recovery)

This unified structure simplifies management and ensures data consistency across all derived volumes.

 Source: Dell PowerStore Administration Guide (Section: Volume Families, Page 97).

The simple performance path in the Dell Unity XT sizer tool uses predefined configurations to streamline the sizing process.

This path considers various parameters to estimate the achievable IOPS rate and overall system performance.

Drive Busy Percentage:

The simple performance path assumes a maximum of 80% drive busy percentage to determine the achievable IOPS rate.

This threshold ensures that the drives are utilized efficiently without overloading, balancing performance and longevity.

Other Percentages:

Lower percentages (50%, 60%, 70%) would be too conservative and might result in under-utilization of the system’s capabilities.

Dell Midrange Storage References:

Dell Unity XT documentation and sizer tool guides provide detailed information on performance metrics and assumptions used for sizing.

Community forums and support resources from Dell Technologies offer additional insights and user experiences.

SSD Wear Alerts in Unity XT:

Dell Unity XT systems monitor SSD wear and issue alerts at various intervals (180, 90, 60, and 30 days) before the predicted end of life.

Action at 30 Days:

At the 30-day alert, the system automatically initiates Proactive Copy Operations to copy data from the wearing SSD to a spare drive, ensuring data integrity and continuity.

Proactive Copy Operations:

This proactive measure helps prevent data loss and maintains system performance by preparing for SSD replacement in advance.

Dell Midrange Storage References:

Dell Unity XT documentation provides detailed guidelines on SSD wear monitoring and the associated proactive measures.

Community forums and support resources from Dell Technologies offer additional insights into system maintenance and proactive data protection.

When sizing a Dell Unity XT solution using the Simple Performance method, parameters such as Read size (KB) and Target IOPS can be defined. The Simple Performance method focuses on understanding the expected IOPS (Input/Output Operations Per Second) and read size to ensure that the system is sized appropriately to meet performance requirements. This approach helps in configuring the storage system to handle the expected workload efficiently.

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To provide the best performance on Dell Unity iSCSI connections, configuring Jumbo frames end-to-end is recommended. Jumbo frames allow for larger packet sizes than the standard 1500 bytes, typically up to 9000 bytes. This reduces the number of packets transmitted, decreases CPU utilization, and improves overall network efficiency. Here’s how to configure Jumbo frames:

Switch Configuration:Enable Jumbo frames on all network switches that will handle iSCSI traffic.

Network Interface Configuration:Configure all network interfaces (NICs) on the storage system and the iSCSI hosts to support Jumbo frames.

End-to-End Consistency:Ensure that Jumbo frames are configured consistently across the entire network path from the storage system to the hosts to avoid fragmentation and performance degradation.

According to Dell best practices for PowerStore solutions, when supporting hosts that use both 100 Gb/s Ethernet (Eth) connectivity and 16 Gb/s Fibre Channel (FC) connectivity, the I/O modules should be populated as follows:

Slot 0:Install the 100 Gb/s Ethernet I/O module. This ensures that the high-speed Ethernet connections are handled by the first slot, which is typically prioritized for network connectivity.

Slot 1:Install the 16 Gb/s Fibre Channel I/O module. This setup leverages the capabilities of the second slot to manage Fibre Channel traffic efficiently.

This configuration ensures optimal performance and adherence to best practices, providing a balanced distribution of network and storage connectivity within the PowerStore system.

The issue arises because File Operations were entered into the PowerSizer tool, but MiB/s (Megabytes per second) was not entered. This causes the tool to translate File Operations into IOPS (Input/Output Operations Per Second) for the cluster and appliance summary details, but since MiB/s was not entered, it does not impact the summary throughput (MiB/s). Here’s the detailed explanation:

File Operations Entry:When file operations are entered, the tool calculates the corresponding IOPS to summarize the workload's impact on the system.

MiB/s Entry Missing:If the MiB/s value is not provided, the tool cannot incorporate this metric into the overall summary, leading to a mismatch where IOPS are calculated but do not affect the MiB/s summary.

Whenonly two SAS ports are available on each Storage Processor (SP) in a Dell Unity XT Disk Processor Enclosure (DPE), therecommended order for connecting DAEsis toalternate DAEs between buses (SAS Bus 0 and SAS Bus 1)to achieve balanced performance and availability.

✅Recommended Order (per Dell EMC Best Practices Guide):

DAE 1→ Connect toSAS Bus 1

DAE 2→ Connect toSAS Bus 0

DAE 3→ Connect toSAS Bus 1

✅Why this order?

Alternating DAEs between buses ensures even distribution of I/O load across the two buses.

It enhances fault tolerance and reduces the risk of performance bottlenecks or single points of failure.

This arrangement follows Dell’s best practice to alwaysbalance the number of DAEs across SAS buseswhenever possible.

❌Why not the other options?

A and D– These do not alternate buses, leading to unbalanced bus usage and potential bottlenecks.

B– Does not balance DAEs evenly across the two buses.

C– Alternates the buses for each DAE, following the recommended best practice for2-port DPE configurations.

✅Documentation Reference:

Dell EMC Unity XT Best Practices Guide– Highlights bus load balancing for optimal performance.

Dell EMC Unity XT Hardware Installation Guide– Provides diagrams and connection orders for DAE cabling.

Dell EMC Unity XT Hardware Overview– Confirms the 2-port DPE recommended configurations.

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Understanding Write-Order-Consistency:

Write-order-consistency ensures that all writes are completed in a specific order to maintain data integrity, particularly important for applications that rely on consistent data states across multiple volumes.

Consistency Groups in PowerStore:

Consistency Groups in Dell PowerStore allow multiple volumes to be managed together as a single entity.

When snapshots are taken of a Consistency Group, all member volumes are captured simultaneously with write-order-consistency, ensuring data integrity across the group.

Other Options:

Volume Groups: Typically used to group volumes for management purposes but do not ensure write-order-consistency for snapshots.

Snapshot Groups: Focus on managing snapshots but without the guaranteed consistency across multiple volumes.

Data Groups: Not a feature in Dell PowerStore specific to this requirement.

Dell Midrange Storage References:

Dell PowerStore documentation provides detailed guidelines on using Consistency Groups for applications requiring write-order-consistent snapshots.

Additional resources from Dell Technologies' support and community forums further validate this feature.

When sizing Dell Unity XT storage solutions, avoiding bottlenecks and improving performance can be achieved by considering the following parameters:

Port Utilization:Ensuring that the storage system’s ports are utilized efficiently helps in distributing the workload evenly across available resources, preventing any single port from becoming a bottleneck.

Workload Types:Understanding and categorizing different workload types (e.g., random vs. sequential, read vs. write) allows for better allocation of resources and tuning of the storage system to handle specific performance requirements.

Within Dell Unity XT storage systems, thin clones are a powerful feature that allows you to create space-efficient copies of a base LUN (Logical Unit Number) without duplicating all of the data, saving significant storage space.

Themaximum number of thin clones per base LUN in Dell Unity XTis16. This limit is documented in the official Dell Unity XT documentation:

According to theDell EMC Unity: Best Practices Guide (Dell Unity OE 5.x)and theDell Unity XT Administrator’s Guide, a base LUN can have up to 16 thin clones.

These thin clones share the same data blocks as the base LUN initially and only consume additional space as they diverge (copy-on-write).

The reason for this limitation is to balance performance and manageability, as thin clones rely on the snapshot engine and copy-on-write technology, which can impact performance if too many clones are active simultaneously.

Key Points:

✅Thin clones are ideal for environments requiring multiple space-efficient copies (e.g., for testing, development, or backup scenarios).

✅They leverage snapshot technology under the hood.

✅16 clones per base LUN strikes a balance between flexibility and system overhead.

The commandsupportshowis used to gather comprehensive data from Brocade switches. This command collects extensive diagnostic information about the switch, including configuration details, hardware status, and various operational statistics. Here's a step-by-step explanation of thesupportshowcommand:

Access the Brocade Switch:Connect to the Brocade switch via SSH or through a console connection.

Enter the Command:Typesupportshowin the command line interface (CLI) and press Enter.

Data Collection:The command will begin collecting a wide array of information from the switch. This includes:

Hardware and firmware versions

Port status and configurations

Zoning information

Error logs and statistics

Environmental data (temperature, power supply status, etc.)

Output Review:The gathered data is typically extensive and can be used for troubleshooting, performance analysis, and ensuring the switch is operating correctly.

Save the Output:The output can be redirected to a file for later review or analysis by technical support teams.

ForNAS (Network Attached Storage)connectivity in Dell Unity XT systems,network availability and redundancyare critical. Dell Unity XT’s best practice for providing thehighest network availabilityfor NAS involvescombining Link Aggregation Control Protocol (LACP) with Fail-Safe Networking (FSN).

✅Why Combine LACP and FSN?

LACP (Link Aggregation Control Protocol)allows multiple physical network links to be combined into a single logical link. This increases bandwidth and provides redundancy at the link level.

FSN (Fail-Safe Networking)provides redundancy at the network path level. It allows two network paths (or groups of links) to be configured with one active and one standby group. If the active path fails, FSN automatically switches to the standby path.

✅Best Practice Benefits:

LACP:Improves link utilization and provides protection against link-level failures.

FSN:Protects against broader network path failures, including switch failures or upstream connectivity issues.

Combined Approach:Providesboth link-level and path-level redundancy, ensuring the highest availability and resiliency for NAS workloads.

✅Documentation Reference:

Dell EMC Unity XT Best Practices Guide (Dell Technologies)– Specifically outlines the recommendation tocombine LACP and FSNfor NAS deployments.

Dell EMC Unity XT Networking Guide– Provides configuration examples and detailed explanations for implementing LACP and FSN in a Unity XT NAS environment.

✅Why not the other options?

A. LACP alone– Improves availability at the link level but not for upstream switch or path-level failures.

B. FSN alone– Provides path-level redundancy but lacks link-level load balancing.

D. Multi-pathing software like PowerPath– Primarily used forblock storage (FC/iSCSI), not NAS.

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Understanding Storage Performance Saturation:

In the Configurations tab of the PowerStore sizing tool, the Storage Performance Saturation field provides crucial information about the overall performance demand placed on the storage solution.

Multi-Appliance Solution Context:

When working with a multi-appliance PowerStore solution, it is important to assess the combined performance demands of all workloads across the appliances.

Aggregate of All Workloads:

The Storage Performance Saturation field shows the aggregate performance demand of all workloads combined. This helps in determining if the current configuration can handle the cumulative IOPS and throughput requirements or if additional resources are needed.

Dell Midrange Storage References:

Dell Technologies documentation on PowerStore and its sizing tools provide detailed guidelines on how to interpret and utilize performance metrics, including the Storage Performance Saturation field.

The Dell Unity XT 380F array is equipped with converged network adapter (CNA) ports, while the Dell Unity XT 880F array features embedded mezzanine ports. These differences in port configurations reflect the varied performance and connectivity options available in different models of the Unity XT series.

 https://www.dell.com/support/manuals/en-id/unity-600/unity_p_replication_config/about-replication?guid=guid-ccd6033f-680e-47ca-bf91-fa3d4221f9d3 &lang=en-us

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Dell Unity XT and DR Design:

For disaster recovery (DR) within a metro distance and zero Recovery Point Objective (RPO), synchronous replication is the preferred method.

Synchronous replication ensures that data is written to both the source and target volumes simultaneously, which requires high performance to minimize latency.

Best Practices for Minimizing Impact on Performance:

Multiple Ports per Controller: While this can improve throughput, it does not directly minimize the latency impact of synchronous replication.

Flash Tier in Hybrid Pool: Including a flash tier in a hybrid pool enhances performance significantly because flash drives offer lower latency and higher IOPS compared to traditional spinning disks. This is critical for synchronous replication scenarios where performance impact needs to be minimized.

Thick Volumes: Using thick volumes can provide consistent performance, but they do not inherently minimize the impact of synchronous replication.

Synchronous Replication Session: Creating the replication session before filling the source storage object with data is a procedural step and does not address performance during active replication.

Dell Midrange Storage References:

Dell Unity XT best practices emphasize the use of flash tiers in hybrid pools to boost performance for demanding operations, including synchronous replication.

Resources from Dell Technologies' documentation on storage-based replication and performance optimization provide detailed insights.

CloudIQ is a cloud-based application that provides frequent, dynamic, and nondisruptive content updates to users. It offers proactive monitoring, predictive analytics, and detailed health scores for Dell storage environments, including PowerStore and Unity systems. CloudIQ helps users maintain optimal system performance by delivering real-time insights and alerts about potential issues before they impact operations. Here’s how CloudIQ benefits users:

Frequent Updates:CloudIQ continuously gathers and analyzes data from connected systems, providing up-to-date information and insights.

Dynamic Content:The tool dynamically adapts to changing conditions in the storage environment, offering relevant recommendations and updates.

Nondisruptive:All updates and insights provided by CloudIQ are nondisruptive, ensuring that there is no interruption to the system’s operations.

The minimum number of drives in a RAID 5 dynamic pool is 5. RAID 5 requires at least 3 drives for data striping with parity, but Dell's implementation in Unity systems requires a minimum of 5 drives to ensure optimal performance and reliability.

SAS Flash 3 drives(also known asRead-Intensive (RI)SSDs in Dell Unity XT environments) are typically rated at3 Drive Writes Per Day (DWPD).

✅What does 3 DWPD mean?

It means that these drives are designed to safely handle writingthree times their entire capacity every dayover their warranty period (usually 5 years).

For example, a 1TB SAS Flash 3 drive can handle up to3TB of writes per daywithout exceeding its endurance specification.

✅Why is this important?

The DWPD metric is a crucial factor in determining whether a drive’s endurance matches the expected workload.

3 DWPDstrikes a balance betweenenduranceandcostin most general-purpose storage workloads.

✅Where is this documented?

TheDell EMC Unity XT Best Practices Guideand theDell EMC Unity XT Drive Specification Guidedetail the DWPD ratings for different flash drive types, including SAS Flash 3 drives.

Dell’s documentation confirms that SAS Flash 3 drives (RI SSDs) are rated at3 DWPD.

Understanding the Calculation Context:In PowerStore, capacity planning for virtualized environments involves forecasting storage requirements based on VM deployments. The formula VM count × Capacity per VM is specifically used to model projected storage consumption before applying efficiency factors.

PowerStore's Capacity Terminology:

Raw Capacity: The total physical capacity of installed drives before accounting for RAID overhead, system metadata, or formatting.

Usable Capacity: The available storage after subtracting RAID overhead, system partitions, and metadata. Represents the logical space presented to the user before data reduction.

Effective Capacity: The logical storage capacity available to applications after accounting for data reduction technologies (deduplication, compression), thin provisioning, and system efficiency. It represents the "logical" data stored per physical byte.

Why "VM count × Capacity per VM" Equals Effective Capacity:

Capacity per VM typically refers to the provisioned (logical) storage allocated to each VM (e.g., a 500GB virtual disk).

Multiplying this by the VM count gives the total logical capacity required by all VMs.

PowerStore uses this product to calculate the "Effective Capacity" requirement. This is the logical capacity the system must support after data reduction efficiencies are applied. It represents the total amount of data the VMs will logically store, which the physical storage (Usable/Raw Capacity) must ultimately hold after deduplication/compression.

Official Dell PowerStore Documentation:The Dell PowerStore: Deployment Planning and Best Practices Guide explicitly defines this calculation:

"Effective Capacity is calculated as: Number of VMs × Average Capacity per VM."

(Source: Dell PowerStore Deployment Planning and Best Practices Guide, Section: Sizing Considerations for Virtualized Environments)

This guide further clarifies that Effective Capacity is the key metric for sizing PowerStore systems in virtualized scenarios, as it represents the logical workload demand the system must satisfy, leveraging its data reduction capabilities to fit onto the physical Usable Capacity.

Conclusion:

Multiplying VM count by Capacity per VM directly yields the Effective Capacity requirement. This represents the logical storage demand placed on the PowerStore system. The physical Usable Capacity must be sufficient to hold this Effective Capacity after data reduction savings are applied. Raw Capacity is unrelated to VM provisioning calculations.

Key References:

Dell PowerStore: Deployment Planning and Best Practices Guide (Current Version) - Definitive source linking VM count × Capacity per VM to Effective Capacity.

Dell PowerStore: Introduction Guide - Explains core concepts of Raw, Usable, and Effective Capacity.

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